This invention relates to multifilament polyester yarns and particularly to improved multifilament polyethylene terephthalate yarns for industrial uses. More particularly, it relates to an improved multifilament polyethylene terephthalate yarn and a new fiber finishing process for polyethylene terephthalate yarns in which novel fiber finish compositions are applied to said yarns. Still more particularly, it relates to a fiber finish composition designed specifically for tire cord processing for polyethylene terephthalate yarns.
Many fiber finish compositions are known. Some are quite specific in composition and relate to specific type fibers. Small changes in fiber finish composition frequently result in tremendous improvements in not only processing but also in end use of the fiber.
Polyester tire yarn finishes generally consist of a combination of a lubricant, an antistat, and several emulsifiers. For example, U.S. Pat. No. 3,687,721 discloses an improved polyester tire yarn treated with a composition comprising decaglycerol tetraoleate, glycerol monooleate, ethoxylated tall oil fatty acid, sulfated glycerol trioleate, ethoxylated alkylamine and hexadecyl stearate. Obviously, maintaining the proper ratio of lubricant, antistat and emulsifiers is essential for consistent performance of the tire yarn. Moreover, many prior art processes require applying a first finish composition during spinning of the yarn and a subsequent overfinish in order to obtain optimum physical properties. Clearly, it would be a significant advance in this art to find a finish that could be used as a single finish for polyester yarn or as an overfinish to provide a tire yarn with excellent properties for use in tires.
Linear high molecular weight polyethylene terephthalate fiber forming polyesters are well known. Such knowledge is well illustrated in U.S. Pat. Nos. 2,465,319; 3,050,533; 3,051,212; 3,427,287 and 3,484,410 as well as many others. Although polyester tire yarn is a highly successful commercial product, even further improvements are desirable. Greater strength is always being sought, and in order to obtain improved thermal stability, lower carboxyl end groups are necessary. Upon obtaining lower carboxyl end groups either by chemical or physical means, adhesion loss of the final textile material to rubber becomes significant. The production of a thermally stable polyester with good adhesion to rubber is, to a great degree, the substance of this invention.